A bicycle is usually provided with two derailleurs, a front one associated with the crankset and a rear one associated with the sprocket assembly. In both cases, the derailleur engages the transmission chain displacing it on toothed wheels having different diameters and different numbers of teeth, so as to obtain different gear ratios. The derailleur, be it the rear or the front, is moved in a direction by the traction action exerted by a normally sheathed inextensible cable (commonly known as Bowden cable) and in the opposite direction by the elastic return action of a spring provided in the derailleur itself. Normally, the direction in which the displacement is carried out by the return spring is that in which the chain passes from a toothed wheel with a greater diameter to a toothed wheel with a smaller diameter, i.e. that of so-called downward gearshifting; vice-versa, the traction action of the control cable occurs in the direction of so-called upward gearshifting, in which the chain moves from a toothed wheel with a smaller diameter to a toothed wheel with a greater diameter. It should be noted that in a front gearshift downward gearshifting corresponds to the passage to a lower gear ratio, whereas in a rear gearshift it corresponds to a higher gear ratio.
The displacement in the two directions of the control cable of a derailleur is obtained through a control device, commonly known as integrated control, mounted so as to be easily manipulated by the cyclist, i.e. normally on the handlebar, in proximity to handgrips thereof. The integrated control also comprises a brake lever for controlling a brake actuation cable of the front or rear wheel. Customarily, the control device of the front derailleur and the brake lever of the front wheel is situated on the left side of the handlebar, and vice-versa the control device of the rear derailleur and the brake lever of the rear wheel is situated on the right side of the handlebar.
In the control device, the control cable is actuated by traction or by release through winding and unwinding on a rotor element, commonly known as cable-winding bush or bobbin, whose rotation is controlled by the cyclist with corresponding control levers.
In integrated control devices of the known type, two distinct ratchet levers control the rotation, in two directions, of the bush and one of the two levers also controls the brake control cable.
Such a device has a support body that when mounted projects from the handlebar towards the front part of the bicycle, on which a first lever is mounted, corresponding to the brake lever, that rotates about a first axis to be actuated by the cyclist towards the handlebar during braking. The same brake lever is also rotatable about a second axis, perpendicular to the first, which controls the rotation of the cable-winding bush about its axis according to a first direction of rotation, to carry out upward gearshifting. Such a rotation substantially follows the movement of the cyclist's hand that pushes the lever inwards, i.e., towards the main axis of the bicycle.
The device also has a second lever rotatable about a third axis, parallel to the second, that when actuated inwardly, causes the released rotation of the cable-winding bush, through the effect of the spring of the derailleur, in a rotational direction opposite the first, resulting in downward gearshifting.
The cable-winding bush has an indexing mechanism associated therewith, which allows rotation of the cable-winding bush in the desired direction during gearshifting and keeps the cable-winding bush in the fixed angular position when the two levers do not act upon it. Both the indexing mechanism and the cable-winding bush are mounted on the first lever and are enclosed by a housing.
The rotation axis of the cable-winding bush, both in normal riding conditions and during braking, belongs to a substantially vertical plane comprising the advancing direction of the bicycle. The control cable of the derailleur that winds/unwinds about the cable-winding bush projects from the housing inwardly (FIG. 16), in a direction substantially perpendicular to said vertical plane, passing through a suitable opening formed in the housing itself. The control cable then reaches the derailleur through an appropriate path along the frame where the control cable is blocked in one or more attachment points.
The arrangement, however, has some drawbacks.
A first drawback noted is that the cable-winding bush, being mounted on the first lever, is a certain distance from the handlebar. Thus the control cable of the gearshift that projects from the housing causes potentially dangerous conditions for the cyclist, for example in the event there is accidental contact with nearby cyclists in a race or, in the event of falls, where the projecting cable entangles in the handlebar of other bicycles involved in the fall.
Another drawback noted is that the housing is not tightly closed since it is provided with an opening for the passage of the control cable, through which dirt or water can enter, that contribute to deteriorate the inner mechanisms of the control and reduce their performances.
A further drawback noted is the unpleasant appearance given to the bicycle by the projecting cables and added drag by reduced aerodynamics.